Abstract : Since the discovery of the ancient harbor of Naples in 2004
during construction work on an underground railway, geoarchaeological
studies undertaken on the archaeological excavation have revealed the
main stratigraphic and paleo-environmental levels of the harbor site near
the Piazza Municipio. However, knowledge of the dynamics and paleoenvironmental
changes in the water column of the harbor, as well as the
processes of transport and deposition of sediments that led to siltation
and infilling of the harbor basin, has been lacking due to the absence of
high-resolution data. To fill these gaps, we have undertaken a threedimensional
study (longitudinal, transverse and vertical) of the harbor
deposits by carrying out geochemical and sedimentological analyses of
four stratigraphic sections of the archaeological excavation. The results
show that after a phase of relative calm during the first half of the 1st
c. AD, siltation of the harbor progressed exponentially up to the 5th c.
AD, when dredging operations were carried out to obtain a water level
sufficient for the development of maritime and harbor activities. We
attribute this acceleration of siltation to a combination of climatic,
anthropic and volcanic factors. Volcanic activity was responsible for a
high-energy, tsunami-type event during the eruption of Vesuvius in 79 AD.
From the 5th c. AD onwards, the harbor basin of Neapolis does not appear
to have been functional as evidenced by its transformation into a lagoon
following coastal progradation. The last stage of infilling was the
development of a flood-dominated fan delta under the combined influences
of climatic cooling in the Early Medieval Cool Period and agro-pastoral
activities in the catchment area of the harbor. Several generations of
paleo-channels, containing flash flood deposits, as well as sheet wash
from sheet floods, are indicative of high environmental instability in
this period.